I can't get a Package on SQL Server Agent to Run. Ideas?

I can't get a Package on SQL Server Agent to Run. Ideas?

I have a Process control containing a mixture of packages which run on a
weekly basis.
When I update a package in Visual studios, it runs perfectly. So I commit
the package to subversion and I update the package in Intergration
services. I check that the package has been updated via the build number.
If I run the process control it will fail at the package. The error I
recieve is this: component "Flat File Source" (471) failed the pre-execute
phase and returned error code 0xC020200E.
However if I then go to intergration services, the package will run fine.
I think it must be a permissions issue, but I am not certain. All i know
is that I have to update packages often and now I am having to go into
intergration services 5/6 times to run different packages that will not
run due to me having updated them.
If anyone has any ideas, please put them forward.
Thanks in advance.